With the help of former Jeep engineer Bob Sheaves and others, Allpar has posted an investigation of what Jeep could use to power the domestic 2018 Wrangler, due to arrive sometime in calendar-year 2017.

The choices are tough for the iconic Jeep, America’s heir to the famed military vehicles — which were far smaller and weighed half as much. On the one hand, higher fuel economy is likely to be needed if fuel prices rise, and if the government continues its demands for efficiency (for national security, balance-of-trade, and, ostensibly, for environmental reasons). On the other, the Jeep must still haul around over two tons of weight, while easily climbing difficult obstacles — and it can’t cheap out on torque.

With that in mind, Wrangler is likely to come with at least two engines, one for economy in Jeeps that will not be challenged much by off-road driving; and one for those who will immediately tackle tough terrain. Indeed, given the popularity of the Ram 1500 Diesel and long-time demands of hard-core Jeepers, a diesel might even be in the cards, and Fiat Chrysler has several options there, too.